1. Field of the Invention
The present invention provides wireless communications, and more particularly, a method for controlling transmission power in a femto base station and an apparatus thereof.
2. Related Art
In a mobile communication system, a femto-cell service has been proposed for the purpose of extending coverage of a base station, enhancing communication quality, providing various communication services, etc. In general, a femto cell refers to a small base station installed at home (hereinafter, referred to as a femto base station) or a service area of the femto base station. A geographical service area of the femto cell has a transmission range of 10 m to 20 m with respect to the femto base station. Such a femto cell service has advantages of low cost of the femto base station, a user's direct and convenient installation of the femto base station, low transmission power, etc. The femto base station can provide a mobile communication service as being connected to a backhaul based on Internet, such as a digital subscriber loop (DSL), a cable modem, etc.
Generally, the femto base station is installed within a service area of a previously installed macro base station. The macro base station is a base station generally installed by a mobile communication service provider, which has a wider service area than the femto base station and is installed in a fixed point. If the femto base station and the macro base station use one channel in a downlink, a downlink signal of a newly installed femto base station is seriously interfered with a downlink signal of a previously installed macro base station. That is, the downlink signal of the newly installed femto base station interferes with a terminal communicating with the macro base station, thereby deteriorating service quality of the whole macro base station. To solve these problems, the related arts have to proposed methods for lowering downlink transmission power of the femto base station. However, if the downlink transmission power of the femto base station is excessively lowered, the service quality may also be deteriorated in terminals of the femto base station.
Further, in the related arts, information exchange of great complexity was needed between the terminal and the femto base station or between the femto base station and the macro base station in determining the transmission power of the femto base station.